Medical imaging device and methods of use

ABSTRACT

Embodiments related to medical imaging devices including rigid imaging tips and their methods of use for identifying abnormal tissue within a surgical bed are disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application claiming the benefitunder 35 U.S.C. §120 of U.S. patent application Ser. No. 14/211,201,entitled “MEDICAL IMAGING DEVICE AND METHODS OF USE,” filed on Mar. 14,2014, which claims priority under 35 U.S.C. §119(e) to U.S. ProvisionalApplication Ser. No. 61/781,601, entitled “IMAGING AGENT FOR DETECTIONOF DISEASED CELLS” filed on Mar. 14, 2013 and U.S. ProvisionalApplication Ser. No. 61/785,136, entitled “IMAGING AGENT FOR DETECTIONOF DISEASED CELLS” filed on Mar. 14, 2013, each of which are hereinincorporated by reference in their entirety.

GOVERNMENT LICENSE RIGHTS

This invention was made with government support under contractIIP-1152489 awarded by the National Science Foundation. The governmenthas certain rights in the invention.

FIELD

Disclosed embodiments are related to medical imaging devices and theirmethods of use.

BACKGROUND

There are over one million cancer surgeries per year performed in theUnited States and nearly 40% of them miss resecting the entire tumoraccording to the National Cancer Institute Surveillance Epidemiology andEnd Results report. For example in breast cancer lumpectomies, failureto remove all of the cancer cells during the primary surgery (positivemargins) occurs approximately 50% of the time and requires secondsurgeries. Residual cancer in the surgical bed is a leading risk factorfor local tumor recurrence, reduced survival rates and increasedlikelihood of metastases. In addition, final histopathology of theresected tumor misses 25% of the residual cancer left in the surgicalbed, which must be addressed with adjuvant medical therapy (e.g.radiotherapy or chemotherapy). This poor performance of pathology isprimarily due to a sampling error since only a small fraction of theentire resection is analyzed.

In a typical solid tumor resection, the surgeon removes the bulk of thetumor and sends it to pathology. The pathologist then samples the bulktumor in a few locations and images a stained section under a microscopeto determine if the surgeon has completely removed all of cancer cellsfrom the patient. Should the pathologist find a portion of the stainedsample with cancer cells bordering ink (a diagnostic known in themedical realm as “positive margin”), the surgeon may be instructed toresect more tissue. However this pathology exercise is a time intensiveprocedure and often takes days for final results to be sent to thephysician. Should a pathology report requiring additional resectionreturn after the patient has completed the initial surgery, this mayrequire the surgeon to perform a second surgery.

In addition to determining clean margins, some surgeries involving theremoval of cancerous tissue adjacent to vital tissue structures, such asneurovascular bundles, require precise localization of abnormal tissueto remove the necessary amount of abnormal tissue while avoiding thesevital tissue structures as much as possible. Surgeries that require suchprecise, real-time localization, may include ovarian cancer debulking,brain cancer resection, sarcoma resection, open prostate tumorresection, esophageal cancer resection, and open colo-rectal tumorresection, among others. In the case of ovarian cancer debulking,survival rates correlate directly with the amount of residual cancerleft in the wound. A patient is deemed “optimally” debulked if no tumorfeatures larger than 1 cm remain at the end of surgery. With ovariancancer debulking surgery, 83% of the time, cancer remains in thepatient, and of those cases, 50% require reexcision surgeries.

Recent advances have been made for in situ observation of residualcancer cells in a tumor resection bed. See, for example, U.S. PatentApplication publication numbers 2009/0299196, 2011/0100471 and2012/0150164, the disclosures of which are incorporated herein byreference in their entirety. The present application is directed to ahand-held device and related technology for performing such in situobservation of residual cancer cells in a tumor resection bed.

SUMMARY

In one embodiment, a handheld medical imaging device may include aphotosensitive detector comprising a plurality of pixels and a rigidimaging tip optically associated with the photosensitive detector. Therigid imaging tip may include a distal end defining a focal plane at afixed focal distance relative to the photosensitive detector, and thedistal end of the rigid imaging tip may be constructed to be placed incontact with tissue and maintain the tissue at the focal plane.

In another embodiment, a hand held medical imaging device may include animaging device body and a rigid imaging tip distally extending from theimaging device body. A distal end of the rigid imaging tip may define afocal plane with a field of view with a lateral dimension between about10 mm to 50 mm inclusively. The rigid imaging tip may also include aproximal portion and a distal portion that is angled by about 25° to 65°inclusively relative to the proximal portion. A length of the distalangled portion may be between about 10 mm to 65 mm, and an optical axismay pass through the rigid imaging tip from the distal end of the rigidimaging tip to the proximal end of the rigid imaging tip.

In yet another embodiment, a hand held medical imaging device mayinclude a photosensitive detector comprising a plurality of pixels and arigid imaging tip optically associated with the photosensitive detector.The rigid imaging tip may include a distal end defining a focal planerelative to the photosensitive detector, and the distal end of the rigidimaging tip may be open. The rigid imaging tip may include at least oneopening on a side of the rigid imaging tip that is sized and shaped toprovide surgical access to the distal end of the rigid imaging tip.

In another embodiment, a hand held medical imaging device may include arigid imaging tip including a proximal portion and a distal portionincluding a distal end. The distal end may include an opening to provideaccess to a surgical bed and one or more supports extending between theproximal portion and the distal portion. A photosensitive detector maybe optically associated with the opening located in the distal end ofthe rigid imaging tip.

In yet another embodiment, a handheld medical imaging device may includea rigid imaging tip including a distal end defining a field of view anda photosensitive detector optically associated with the rigid imagingtip. A first illumination source may be adapted and arranged to providelight with a first wavelength to the distal end of the rigid imagingtip. A second illumination source may also be adapted and arranged toprovide light with a second wavelength to the distal end of the rigidimaging tip. The first wavelength and the second wavelength may bedifferent. Additionally, the first illumination source and the secondillumination source may be adapted to alternatingly pulse.

In another embodiment, a handheld medical imaging device may include arigid imaging tip including a distal end defining a focal plane with afield of view. A photosensitive detector may be optically associatedwith the rigid imaging tip and an aperture may be located between thephotosensitive detector and the rigid imaging tip. The aperture may havea diameter between about 5 mm to 15 mm inclusively. The handheld medicalimaging device may also include a first illumination source adapted andarranged to provide between about 10 mW/cm² to 200 mW/cm² of light atthe focal plane, wherein the light has a first wavelength between about300 nm to 1,000 nm.

In yet another embodiment, a method for identifying abnormal tissue mayinclude: providing a first light comprising a first excitationwavelength to a surgical bed; collecting a fluorescence signal from thesurgical bed using a photosensitive detector; comparing the fluorescencesignal to an abnormal tissue threshold to identify abnormal tissue; andindicating one or more locations of the identified abnormal tissue on ascreen.

In another embodiment, a method for identifying abnormal tissue mayinclude: illuminating a surgical bed with a first light comprising afirst excitation wavelength of a imaging agent using a firstillumination source; illuminating the surgical bed with a second lightcomprising a second wavelength different from the first excitationwavelength using a second illumination source; and collecting a signalfrom the surgical bed using a photosensitive detector.

In yet another embodiment, a method for identifying abnormal tissue mayinclude: illuminating the surgical bed with ambient light; illuminatinga surgical bed with a first light comprising a first excitationwavelength of an imaging agent by pulsing a first illumination source;collecting a first signal from the surgical bed corresponding to ambientlight using a photosensitive detector including a plurality of pixels;and collecting a second signal from the surgical bed corresponding toambient light and a pulse of the first illumination source.

It should be appreciated that the foregoing concepts, and additionalconcepts discussed below, may be arranged in any suitable combination,as the present disclosure is not limited in this respect. Further, otheradvantages and novel features of the present disclosure will becomeapparent from the following detailed description of various non-limitingembodiments when considered in conjunction with the accompanyingfigures.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are not intended to be drawn to scale. In thedrawings, each identical or nearly identical component that isillustrated in various figures may be represented by a like numeral. Forpurposes of clarity, not every component may be labeled in everydrawing. In the drawings:

FIG. 1A is a schematic representation of a surgical bed being imagedwith decreased magnification;

FIG. 1B is a schematic representation of a surgical bed being imagedwith increased magnification;

FIG. 2A is a schematic side view of a closed tip handheld medicalimaging device;

FIG. 2B is a schematic rear perspective view of the closed tip handheldmedical imaging device of FIG. 2A;

FIG. 2C is a schematic side perspective view of the closed tip handheldmedical imaging device of FIG. 2A;

FIG. 3A is a cross sectional view of the closed tip handheld medicalimaging device of FIG. 2A;

FIG. 3B is perspective cross sectional view of the closed tip handheldmedical imaging device of FIG. 2A;

FIG. 4A is a schematic side view of an open tip handheld medical imagingdevice;

FIG. 4B is a schematic rear perspective view of the open tip handheldmedical imaging device of FIG. 4A;

FIG. 4C is a schematic front perspective view of the open tip handheldmedical imaging device of FIG. 4A;

FIG. 5A is a schematic cross sectional view of the open tip handheldmedical imaging device of FIG. 4A;

FIG. 5B is perspective cross sectional view of the open tip handheldmedical imaging device of FIG. 4A;

FIG. 6 is a schematic rear perspective view of a rigid imaging tipincluding a restraining element;

FIG. 7 is a schematic rear perspective view of a rigid imaging tipincluding an orienting feature;

FIG. 8A is a schematic rear perspective view of a light box;

FIG. 8B is a schematic side view of the light box of FIG. 8A;

FIG. 8C is a schematic perspective view of the light box of FIG. 8A;

FIG. 8D is a schematic cross sectional view of the light box of FIG. 8A;

FIG. 9A is a flow diagram of one embodiment of a method for operating amedical imaging device;

FIG. 9B is a flow diagram of one embodiment of a method for operating amedical imaging device;

FIG. 9C is a flow diagram of one embodiment of a method for operating amedical imaging device;

FIG. 10A is a graph of fluorescence intensity of a fluorphore fordifferent excitation wavelengths;

FIG. 10B is a graph of fluorescence intensity of a fluorphore fordifferent excitation wavelengths;

FIG. 11A is an image taken with room light and a fluorescence signal;

FIG. 11B is an image taken with room light;

FIG. 11C is an image generated by subtracting the imaging taken withroom light from the image taken with room light and a fluorescencesignal;

FIG. 12A is an image captured with an imaging device showing a desiredfield of view and portions outside the field of view;

FIG. 12B is a graph depicting the photon counts for pixels within thefield of view and outside the field of view;

FIG. 12C is an image with the pixels outside the field of view set to adesired value;

FIG. 13A is an image of a fluoroscopic standard while in focus;

FIG. 13B is an image of a fluoroscopic standard while out of focus;

FIG. 14A is a graph of photon counts for a line taken across FIG. 13Acorresponding to an in focus image;

FIG. 14B is a graph of photon counts for a line taken across FIG. 13Bcorresponding to an out of focus image;

FIG. 15A is a close-up of a portion of the graph presented in FIG. 14Acorresponding to an in focus image;

FIG. 15B is a close-up of a portion of the graph presented in FIG. 14Bcorresponding to an out of focus image;

FIG. 16A is an image of a tumor from a dog with naturally occurring lungcancer injected with LUM015;

FIG. 16B is an image of normal lung tissue from a dog with naturallyoccurring lung cancer;

FIG. 17A is a raw image taken using LUM015 of a mouse-sarcoma surgicalbed after surgery in a mouse following IV injection of LUM015;

FIG. 17B is the same image as FIG. 17A analyzed by a detection system tohighlight regions containing residual cancer;

FIG. 17C the same image as FIG. 17A analyzed by a detection system tohighlight regions containing residual cancer;

FIG. 18A is a raw image of a surgical bed;

FIG. 18B is the same image as FIG. 18A analyzed by a detection system tohighlight regions containing abnormal tissue; and

FIG. 19 is an exemplary screenshot of an interface that might be used topresent images highlighting regions containing abnormal tissue within asurgical bed.

DETAILED DESCRIPTION

The inventors have recognized that advances in cancer targetingmolecular imaging agents have enabled the detection of small clusters ofresidual cancer on a background of healthy tissue. However, visuallyidentifying cancerous tissue on the millimeter to submillimeter scaleduring a surgery is difficult even with these imaging agents. Therefore,the inventors have recognized a need for medical imaging devices capableof reliably detecting millimeter to sub millimeter residual cancer cellsduring surgery to facilitate the removal of this cancerous tissue. Suchan imaging device may help to reduce the number of required follow-upsurgeries due to cancerous tissue being left within a surgical bed.

In view of the above, the inventors have recognized the benefitsassociated with a handheld medical imaging device for use with anappropriate imaging agent. In some embodiments, the medical imagingdevice may provide sufficient illumination of an excitation wavelengthof the imaging agent to generate a fluorescence signal from the imagingagent that exceeds instrument noise of the imaging device. In someembodiments, the illumination provided by the medical imaging device mayalso result in an autofluorescence signal from healthy tissue. Themedical imaging device may also detect abnormal tissue at sizes rangingfrom centimeters to single cells with sizes on the order of 10micrometers to tens of micrometers. Other size scales are also possible.As described in more detail below, in some embodiments, it may bedesirable for the medical imaging device to be able to image a largefield of view in real-time and/or be relatively insensitive to humanmotions inherent in a handheld device as well as natural motions of apatient involved in certain types of surgery such as breast cancer andlung cancer surgeries. The imaging device may either be used for imagingsurgical beds, such as tumor beds, or it may be used for imaging alreadyexcised tissue as the disclosure is not so limited.

In one embodiment, a medical imaging device may include a rigid imagingtip including a distal end defining a focal plane at a fixed distancefrom an optically associated photosensitive detector. For example, adistally extending member may define at its distal end a focal plane ofthe photosensitive detector. Depending on the embodiment, opticsassociated with the photosensitive detector may either fix a focus ofthe photosensitive detector at the focal plane located at the distal endof the rigid imaging tip, or they may permit a focus of thephotosensitive detector to be shifted between the focal plane located atthe distal end of the rigid imaging tip and another focal plane locatedbeyond the distal end of the rigid imaging tip. While any appropriatephotosensitive detector might be used, exemplary photosensitivedetectors include a charge-coupled device (CCD) detector, acomplementary metal-oxide semiconductor (CMOS) detector, and anavalanche photo diode (APD). The photosensitive detector may include aplurality of pixels such that an optical axis passes from the focalplane of the rigid imaging tip to the photosensitive detector.

Depending on the embodiment, a medical imaging device can also includeone or more light directing elements for selectively directing lightfrom an illumination source comprising an excitation wavelength of animaging agent towards a distal end of the device while permittingemitted light comprising an emission wavelength of the imaging agent tobe transmitted to the photosensitive detector. In one aspect, a lightemitting element comprises a dichroic mirror positioned to reflect lightbelow a wavelength cutoff towards a distal end of an associated imagingtip while permitting light emitted by the imaging agent with awavelength above the wavelength cutoff to be transmitted to thephotosensitive detector. However, it should be understood that otherways of directing light towards a distal end of the device might be usedincluding, for example, fiber optics, LED's located within the rigidtip, and other appropriate configurations.

An imaging device may also include appropriate optics to focus lightemitted from within a field of view of the device onto a photosensitivedetector with a desired resolution. In order to provide the desiredresolution, the optics may focus the emitted light using any appropriatemagnification onto a photosensitive detector including a plurality ofpixels. In some embodiments, the magnification is such that each pixelmay have a field of view that corresponds to a single cell or only aportion of a single cell. Depending on a size of the individual pixels,the optics may either provide magnification, demagnification, or nomagnification as the current disclosure is not so limited. For example,in an embodiment where the pixels of a photosensitive detector aresmaller than the cells being imaged, the optics may demagnify thedevice's field of view to provide a desired field of view for each pixelsuch as for example 4 pixels per cell. While embodiments in which afield of view of each pixel is equal to or less than a single celldescribed above, embodiments in which the field of view of each pixel islarger than a single cell are also contemplated.

Without wishing to be bound by theory, a typical cancer cell may be onthe order of approximately 15 μm across. In view of the above, anoptical magnification of the optics within a medical imaging device maybe selected such that a field of view of each pixel may be equal to orgreater than about 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 10 μm, 15 μm, 30 μm, orany other desired size. Additionally, the field of view of each pixelmay be less than about 100 μm, 50 μm, 40 μm, 30 μm, 20 μm, 10 μm, or anyother desired size scale. In one specific embodiment, the field of viewper pixel may be between about 5 μm and 100 μm inclusively. In anotherembodiment, the field of view per pixel may be between about 5 μm and 50μm inclusively.

In some instances, it may be desirable to identify both small regions ofabnormal tissue as well as larger regions of abnormal tissue. This maybe of particular benefit in surgeries such as ovarian cancer surgerywhere a surgical cavity may have a diameter of 20 cm. Therefore, in oneembodiment, optics present within the imaging device may be used toalter a magnification of the emitted light captured by thephotosensitive detector between a higher magnification setting used todetect micrometer scale abnormal tissues as well as a lowermagnification setting where the medical imaging device may be used in astandoff mode to observe large portions of a surgical cavity. Dependingon the embodiment, a field of view of the pixels of a photosensitivedetector may be selectively set between about 5 μm and 100 μm. Ininstances where the medical imaging includes a rigid imaging tipdefining a fixed focal plane at a fixed distance from an associatedphotosensitive detector, the above embodiment may correspond to shiftingthe focus of the photosensitive detector from the fixed focal plane to asecond focal plane located at a second distance beyond the distal end ofthe rigid imaging tip to enable use of the device in a standoff mode forimaging tissue located beyond the end of the medical imaging device.This second focal plane may either be located at a fixed distance, or itmay be variably set using an appropriate focusing element. Further, thefocus of the medical imaging device may either be controlledautomatically or it may be controlled manually as the disclosure is notlimited in this fashion.

As noted above, it may be desirable to improve the resolution anddecrease the sensitivity of the medical imaging device to naturalmotions of a patient during surgery. This may be of particular benefitin surgeries such as breast lumpectomies and lung cancer surgeries wherenatural movements of the patient may interfere with imaging. Withoutwishing to be bound by theory, one way to improve resolution anddecrease sensitivity to natural motions of a patient is to fix adistance between the tissue being examined and the photosensitivedetector being used to capture signals from that tissue. Therefore, inembodiments, the medical imaging device may be adapted and arranged toprovide a fixed distance between tissue being examined and thephotosensitive detector. This might be provided in any number of waysincluding, for example, by constructing the rigid imaging tip such thatit may be placed in contact with the tissue being examined. The imagingtip may be sufficiently rigid such that it may be pressed against thetissue while retaining its shape. Therefore, the rigid imaging tip mayact as a spacer to provide a fixed distance between the tissue and thephotosensitive detector. Additionally, since the rigid imaging tip maybe pressed against the tissue being examined, it may resist both lateraland out of plane movements of the tissue due to patient movements.

In one embodiment, a rigid imaging tip may correspond to a closedimaging tip. In such an embodiment, a distal end of the rigid imagingtip may be a substantially flat window, such that it defines a focalplane of an associated photosensitive detector. Without wishing to bebound by theory, when the flat surface of the distal end is pressedagainst tissue being imaged, the tissue may be compressed to conform toa shape of the closed imaging tip. This in turn may position the tissueadjacent to the focal plane of the photosensitive detector to provide afixed distance between the tissue being examined and the photosensitivedetector. In one particular embodiment, the flat distal end maycorrespond to a flat window disposed on, or integrated into, a distalend of the rigid imaging tip. The window may be transparent to one ormore preselected wavelengths, or spectrum of wavelengths, such as anexcitation wavelength and emission wavelength of a desired imagingagent. Thus, tissue may be positioned in, or proximate next to, adesired focal plane while permitting light comprising an excitationwavelength and/or emission wavelength of the imaging agent to pass outof and back into the imaging device. In another embodiment, the distalend of the imaging tip may be a ring defining a circular opening andfocal plane though other shapes might be used as well.

To facilitate insertion of a rigid imaging tip into a surgical cavity,in some embodiments, it may be desirable for the rigid imaging tip toinclude a distal portion that is angled relative to a proximal portionof the rigid imaging tip or relative to the body of the hand helddevice. An optical path of the device may pass from a distal end of therigid imaging tip through both the distal and proximal portions of therigid imaging tip to an optically associated photosensitive detector. Inorder to bend the optical path around the angled distal and proximalportions, the rigid imaging tip may include an appropriate opticalcomponent located between the proximal portion and the distal portion ofthe rigid imaging tip, such as a mirror or prism, that is adapted tobend the optical path around the angled portion of the rigid imagingtip. In one specific embodiment, the rigid imaging tip may have a distalend defining a focal area with a lateral dimension of about 10 mm to 50mm inclusively, 15 mm to 35 mm inclusively, 25 mm to 35 mm inclusively,or any other appropriate range of dimensions. The distal portion of thetip is also angled relative to the proximal portion by an angle ofbetween about 25° to 65° inclusively, 35° to 55° inclusively, or anyother appropriate angle. Additionally, the distal portion of the rigidimaging tip may have a length along the optical path that is about 10 mmto 65 mm inclusively, 25 mm to 65 mm inclusively, or any otherappropriate length. Such an embodiment may be particularly suited foruse in breast surgeries, whereby the device can be rotated by hand toeasily position the focal plane relative to the surgical bed.

In other embodiments, it may be desirable to facilitate imaging of asurgical bed, and simultaneous surgical access. In one such embodiment,the rigid imaging tip may include a distal end including an openingdefining the focal plane, that is adapted to be positioned adjacent totissue during use. The imaging tip may also include one or more openingslocated on a side of the rigid imaging tip to provide access to theopening in the distal end of the rigid imaging tip. The one or moreopenings on the side of the imaging tip may either be formed in asidewall of the rigid imaging tip or between one or more supportsextending from a proximal portion of the rigid imaging tip to a distal,tissue-engaging portion of the rigid imaging tip. In one embodiment, thedistal ring defining the focal plane is supported by a single strut, andthe opening defined by the ring is accessible from any side, beingobstructed only by the single strut. In such cases, a surgeon may beable to both image abnormal tissue located within a field of view of therigid imaging tip as well as simultaneously perform surgery on theidentified abnormal tissue through the open distal end and the one ormore side openings of the rigid imaging tip.

In embodiments, the medical imaging device may be associated with and/orcoupled to one or more illumination sources. For example, a firstillumination source may be adapted and arranged to provide lightincluding a first wavelength to a light directing element that reflectslight below a threshold wavelength towards a distal end of a rigidimaging tip and transmits light above the threshold wavelength. However,other ways of directing light from the one or more illumination sourcestoward the distal end of the rigid imaging tip including fiber opticsand LED's located within the device or rigid imaging tip might also beused. Regardless, or how the light is directed, the first wavelength maybe selected such that it is below the threshold wavelength and thus willbe reflected towards the distal end of the rigid imaging tip toilluminate the device's field of view. The illumination source mayeither be a constant illumination source or a pulsed illumination sourcedepending on the particular embodiment. Additionally, the firstwavelength may be selected such that it corresponds to an excitationwavelength of a desired imaging agent. It should be understood that thespecific wavelength will be dependent upon the particular imaging agent,optics, as well as the sensitivity of the photosensitive detector beingused. However, in one embodiment, the first wavelength may be about 300nm to 1,000 nm, 590 nm to 680 nm, 600 nm to 650 nm, 620 nm to 640 nm, orany other appropriate range of wavelengths depending on the particularimaging agent being used. Additionally, the first illumination sourcemay be adapted to provide between about 10 mW/cm² to 200 mW/cm² at adesired focal plane for imaging tissue within a surgical bed, thoughother illumination intensities might also be used. For example, a lightintensity of 50 mW/cm² to 200 mW/cm², 100 mW/cm² to 200 mW/cm², 150mW/cm² to 200 mW/cm² could also be used. Depending on the particularimaging agent being used, the various components of the medical imagingdevice may also be constructed and arranged to collect emissionwavelengths from an imaging agent that are about 300 nm to 1,000 nm, 590nm to 680 nm, 600 nm to 650 nm, 620 nm to 640 nm, or any otherappropriate range of wavelengths.

In order to help reduce spherical aberrations and improve a depth offield of an image, a medical imaging device may include an appropriatelysized aperture. However, smaller aperture sizes result incorrespondingly lower signals reaching an associated photosensitivedetector. Therefore, depending on the signal magnitude of an imagingagent versus an autofluorescence signal of surrounding normal tissue aswell as the photosensitive detector ground and dark noise, it may benecessary to increase the illumination provided by an associatedillumination source. In one embodiment, an appropriate combination ofaperture size and illumination source include an illumination source asnoted above and an aperture located between the photosensitive detectorand the rigid imaging tip with a diameter between about 5 mm to 15 mminclusively to provide an image side f number between about 1.5 to 4.5inclusively. In a related embodiment, the aperture might be sized toprovide an f number between about 3 to 3.5 inclusively.

In one specific embodiment, an imaging device includes an aperture witha width of about 10.6 mm corresponding to an image side f number ofabout 3.4. The imaging device also includes a light source including a50 W red LED adapted to emit about 5 W of light at 630 nm. In thisembodiment, the light incident on a surgical bed is about 60 mW/cm². Theassociated light directing element is a dichroic mirror with awavelength cutoff threshold of about 660 nm that reflects light withwavelengths less than that cutoff threshold towards a distal end of theimaging device. While a particular aperture, cutoff threshold, andillumination source are described above, it should be understood thatother ranges of aperture sizes, f numbers, wavelengths, and cutoffthresholds are also contemplated as previously discussed.

In some instances, in order to facilitate surgery while imaging asurgical site, it may be desirable to enable imaging of objects and/orhealthy tissue in addition to abnormal tissue marked with an imagingagent within a surgical site. In such an embodiment, an imaging devicemay include a second illumination source constructed and arranged toprovide light to the surgical site. In one embodiment, the secondillumination source may simply be ambient light incident on a surgicalsite due to an imaging device being operated in a standoff mode where itis not in contact with the tissue or from the device including openingsthrough which the ambient light may enter. In another embodiment, asecond illumination source may provide light with one or morewavelengths, or a spectrum of wavelengths, that are greater than acutoff wavelength of the light directing element and an associatedexcitation wavelength of the imaging agent. Therefore, light from thesecond illumination source may illuminate tissue located within a fieldof view of the device and pass through the light directing elementtowards an associated photosensitive detector. This may help to generate“white light” images during use. The first illumination sourcecorresponding to an excitation wavelength of the imaging agent mayeither be operated in a constant mode or it may be pulsed during imagingto facilitate isolating the florescence signal as described in moredetail below.

Without wishing to be bound by theory, in some instances, identifying afluorescence signal from abnormal tissue marked with an imaging agentfrom autofluorescence signals emitted from surrounding healthy tissuemay be difficult. For example, an emission signal from a marked abnormaltissue may become convoluted with an autofluorescence signal making itmore difficult to identify. Some types of tissue that are known togenerate large fluorescence signals that might interfere withidentification of residual cancer during intraoperative imaging mayinclude, but are not limited to, tissues such as bone and skin. Hence, asystem that can isolate a fluorescence signal that arises from acancer-targeting imaging agent from a background fluorescence signalthat arises due to native fluorescent agents may be advantageous.

In one embodiment, mitigating interference from autofluorescence oftissue within a surgical site may involve the use of a firstillumination source and a second illumination source coupled to amedical imaging device. The first and second illumination sources mayeither be separate devices, or they may be combined as noted above. Themedical imaging device may include a distally extending imaging tipwhere a distal end of the imaging tip defines a field of view of thedevice. The first illumination source and the second illumination sourcemay be coupled to the imaging device such that they provide light to thedistal end of the imaging tip. For example, a dichroic mirror may bepositioned along an optical path such that it directs light from thefirst and second illumination sources to the distal end of the imagingtip. Alternatively, other methods of directing light from the first andsecond illumination sources towards the distal end of the imaging mightalso be used as described above. The first illumination source mayproduce a first light with a first wavelength that corresponds to anexcitation wavelength of a desired imaging agent. The secondillumination source may produce a second light with a second wavelengthcorresponding to a different excitation wavelength of the desiredimaging agent. Additionally, the first illumination source and thesecond illumination source may alternatingly pulse to induce differentfluorescence signals from tissue located within the field of view.Depending on the embodiment, the first and second illumination sourcesmay alternatingly pulse for each exposure period of a photosensitivedetector or each pulse may last for multiple exposures of aphotosensitive detector as the disclosure is not so limited.

In embodiments where two or more illumination sources are used, theillumination sources may correspond to either a single illuminationsource or multiple illumination sources as the disclosure is not solimited. For example, a single illumination source might provide lightincluding multiple wavelengths. Filters and other appropriate opticalcomponents could then be used to provide the separate desiredwavelengths of light to the appropriate locations on the medical imagingdevice.

Without wishing to be bound by theory, an imaging agent separatelyexposed to two different excitation wavelengths will exhibit apredictable rise or drop in the resulting fluorescence signal intensity.Therefore, a change between the fluorescence signals captured by a pixelof a photosensitive detector in response to excitation from two separateillumination sources may be compared to the expected change in thefluorescence signal for the imaging agent to identify abnormal tissuemarked by the imaging agent. Conversely, pixels that do not exhibit theexpected change in the fluorescence signal may be identified as normaltissue. For example, when LUM015 is used to mark a desired tissue, afirst excitation wavelength between about 590 nm and 670 nm as well as asecond excitation wavelength of between about 510 nm and 590 nm might beused. LUM015 includes the fluorochrome CY5 and is described genericallyin U.S. Publication Number 2011/0104071 and also in U.S. applicationSer. No. 61/781,601, the disclosures of which are incorporated herein byreference. LUM033 also includes the fluorochrome CY5 and can likewise beused to mark a desired tissue, using the same first excitationwavelength of between about 590 nm and 670 nm and second excitationwavelength of between about 510 nm and 590 nm. Lum 33 also is describedgenerically in U.S. Publication Numbers 2011/0104071 and 2012/0150164.It is similar to LUM015 in that it has a pharmacokinetic modifier and aCy5 fluorochrome, but it does not have a quencher and an enzyme cleavagesite. Instead, it relies on a pharmacokinetic modifier that clears theimaging agent preferentially from the healthy tissue leaving the cancercells and/or tumor associated inflammation cells labeled. It should beunderstood that appropriate excitation wavelengths will vary fordifferent imaging agents and that the disclosure in some aspects is notlimited to any particular first and second excitation wavelengths.

As noted previously it may be desirable to provide approximately 2 mmtumor margins that are free of residual cancer cells. Therefore, in someembodiments, it may be beneficial to use an imaging agent that providesa detection depth on the order of about 1 mm to 2 mm from the surgicalbed surface to provide for imaging of cells located at the surgical bedsurface to the desired detection depth of about 1 mm to 2 mm. Withoutwishing to be bound by theory, by selecting an imaging agent withappropriate excitation and fluorescence emission wavelengths, thepenetration depth of the imaging agent may be limited to a desired rangesuch as about 1 mm to 2 mm inclusively as noted above. Therefore, asurgeon may be confident that the detected signal corresponds to tissuelocated within about 1 mm to 2 mm from the surgical bed surface. Thisenhanced depth specificity may enable a surgeon to resect a smalleramount of tissue which is beneficial for multiple reasons. Again,without wishing to be bound by theory, light with wavelengths in the farred spectrum corresponding to wavelengths of about 710 nm to 850 nm mayoffer penetration depths of about 1 mm to 2 mm in tissue, thoughwavelengths between about 300 nm and 1,000 nm could also be used.Consequently, imaging agents that operate in the far red spectrum mayprovide the desired penetration depths of about 1 mm to 2 mm from asurgical bed surface. Therefore, in some embodiments, a medical imagingdevice may be used with an imaging agent that operates in the far redspectrum. However, it should be understood that an imaging agent mayprovide a detection depth that is either larger or smaller than 2 mm asthe disclosure is not so limited. For example, imaging agents withexcitation and fluorescence emission wavelengths capable of providingdetection depths between about 1 mm to 5 mm might also be used. Itshould be understood that excitation wavelengths with penetration depthsgreater than the desired penetration depth might be used since theemitted fluorescence signal would still be limited to the desiredpenetration depth. Therefore, for example, a device might be operatedwith an imaging agent with an excitation wavelength at one wavelengthand a separate fluorescence wavelength between about 590 nm and 850 nm.

An exemplary imaging agent capable of providing the desired detectiondepths noted above is LUM015 (and other such agents described in U.S.Patent Publication Number 2011/0104071) which employ the fluorophoreCY5. Other appropriate fluorophores that might be included in an imagingagent include, but are not limited to, Cy3, Cy3.5, Cy5, Alexa 568, Alexa546, Alexa 610, Alexa 647, ROX, TAMRA, Bodipy 576, Bodipy 581, BodipyTR, Bodipy 630, VivoTag 645, and Texas Red. Of course, one of ordinaryskill in the art will be able to select imaging agents with fluorophoressuitable for a particular application.

The Lum Imaging agents presently used are the subject of patentapplication Ser. No. ______, filed on even date herewith, and entitledIMAGING AGENT FOR DETECTION OF DISEASED CELLS, the disclosure of whichis incorporated herein by reference.

In view of the desired detection depths, an imaging device may beoptimized to take into account both the desired imaging depth as well asanticipated natural movements of a patient during surgery. For example,movements of the chest during lung cancer and breast lumpectomysurgeries are to be expected. Consequently, the depth of field of animaging device may be between about 0.1 mm and 10 mm inclusively, 0.1 mmto 5 mm inclusively, or 1 mm to 5 mm inclusively. However, it should beunderstood that other depths of field both larger and smaller than theranges noted above are also contemplated.

The medical imaging devices described herein may be used in any numberof ways. However, in one embodiment, the medical imaging device may beused to identify abnormal tissue located within a surgical bed. This mayinclude providing a first light including a first excitation wavelengthof a desired imaging agent to the surgical bed. The first excitationwavelength may result in a fluorescence signal being emitted fromabnormal tissue marked with an appropriate imaging agent such as, forexample, LUM015. An appropriate photosensitive detector including aplurality of pixels may collect the emitted fluorescence signal forcomparison to an abnormal tissue threshold. Pixels collectingfluorescence signals greater than the abnormal tissue threshold may beidentified as corresponding to abnormal tissue.

Depending on the particular embodiment, an abnormal tissue threshold maybe determined in a number of ways. In instances where the fluorescencesignal associated with surrounding healthy tissue and a particularmarked abnormal tissue is well-established, the abnormal tissuethreshold might simply correspond to a predetermined numbercorresponding to that type of abnormal tissue marked with a particularimaging agent. For example, the abnormal tissue threshold may be16.6×10¹⁰ counts/s/cm² for breast cancer surgery performed using LUM015.In contrast, in instances where autofluorescence signals andfluorescence signals of a marked abnormal tissue may vary widely betweenindividuals, an abnormal tissue threshold may be determined by firstmeasuring a normal tissue signal on a healthy section of tissue. Anabnormal tissue threshold may then be defined as having a signalintensity that is greater than the normal tissue signal by apredetermined value. For example, a surgeon might image a section ofnormal tissue and a controller of the imaging device may analyze theimage to both determine a normal tissue signal and an appropriateabnormal tissue threshold. This may be of particular benefit ininstances where an imaging device collects both fluorescence signalsfrom an imaging agent as well as autofluorescence signals from tissuewithin a surgical bed.

In addition to the above, in some embodiments a medical imaging devicemay also include a size threshold for determining if a fluorescentsignal that is greater than an abnormal tissue threshold isstatistically significant. This may help to identify whether or not anabnormal tissue marked with an imaging agent is present or if abnormaltissue larger than a desired size is present. For example, a controllerof a medical imaging device may identify one or more contiguous pixelsexhibiting a fluorescence signal greater than an abnormal tissuethreshold. However, if a size of the identified one or more contiguouspixels is less than a size threshold, the controller may disregard thissignal as being statistically insignificant and will not identify thetissue as being abnormal tissue. For example, if a size of a regionexhibiting a fluorescence signal is less than the size of a cell, asystem may determine that the detected signal is not associated withabnormal tissue. Alternatively, it may only be desirable to removeportions of abnormal tissue that are above a certain size threshold forpractical reasons such as limited surgical time. Therefore, depending onthe particular application, an appropriate size threshold may be lessthan a size of a single cell or multiple cells as the current disclosureis not so limited. For instance, an appropriate size threshold may bebetween about 5 μm to 160 μm, 5 μm to 100 μm, or 5 μm to 50 μm. Othersize thresholds both greater than and less than those noted above arealso contemplated and will depend on the particular imaging agent andtissue being examined.

As described above, a controller associated with a medical imagingdevice may process the collected raw images to identify the presence ofabnormal tissue within a field of view of the device using appropriatesignal and/or size thresholds. In addition to determining the presenceof abnormal tissue within a field of view, the controller may alsooutput the collected images to a screen, or other viewing device forviewing by a user. The controller may then specifically indicate thelocation(s) of the previously identified abnormal tissue on the screenin order to bring them to a surgeon's attention. The location(s) of theidentified abnormal tissue may be indicated on the screen in anyappropriate manner including, for example, highlighting the locations ofthe identified abnormal tissue and/or a perimeter of the identifiedabnormal tissue using an appropriate color, increased contrast,increased intensity, or other appropriate way of highlighting thedesired features on a screen or output device. Alternatively, geometricshapes superimposed onto the image might be used to indicate thelocation of identified abnormal tissue on a screen or other outputdevice. Appropriate geometric shapes may include, but are not limitedto, an arrow, or other shape, pointing to the identified abnormal tissueor a shape such as a circle, a square, a rectangle, a non-symmetricclosed loop, or other appropriate shape superimposed onto the screensuch that it encompasses a perimeter of the identified abnormal tissue.In some embodiments, highlighting might be used to indicate abnormaltissue with a size greater than a predetermined size limit and geometricshapes might be used to indicate abnormal tissue with a size less thanthe predetermined size limit. In some embodiments, both highlighting andgeometric shapes are used to indicate the location of identifiedabnormal tissue with a size that is less than a predetermined sizelimit. Depending on the particular use, the predetermined size limit maybe less than about 1 mm², 2 mm², 3 mm², 4 mm², or any other appropriatedimension. Therefore, it should be understood that other predeterminedsize limits both greater than and less than those noted above are alsopossible. Other ways of indicating the location of abnormal tissue arealso possible. While specific ways of indicating the presence ofidentified abnormal tissue on a screen or other output device aredescribed above, the disclosure is not limited to the specificembodiments described herein and should instead be interpreted asencompassing any appropriate method of indicating the presence ofabnormal tissue on a screen or other output device.

While various combinations of optical components and illuminationsources are described above and in reference to the figures below, itshould be understood that the various optical components such asfilters, dichroic mirrors, fiber optics, mirrors, prisms, and othercomponents are not limited to being used with only the embodiments theyare described in reference to. Instead these optical components may beused in any combination with any one of the embodiments describedherein.

Turning now to the figures, several specific embodiments are describedin more detail. It should be understood that the specific featuresdescribed in regards to the various embodiments are not limited to onlythose embodiments. Instead, the various embodiments and features may becombined in various ways as the disclosure is not limited.

FIGS. 1A and 1B depict schematic representations of exemplaryembodiments for components of a medical imaging device 2. The medicalimaging device may include a rigid imaging tip 4 at least partiallydefined by a distally extending member, frustoconical cylinder or otherhollow structure. The rigid imaging tip 4 may be constructed andarranged to be held against tissue to fix a focal length of the medicalimaging device relative to the tissue. As depicted in the figures, therigid imaging tip 4 may also include an open distal end that defines afield of view 6. The medical imaging device 2 may also include opticssuch as an objective lens 8, an imaging lens 10, and an aperture 16. Theoptics may focus light from the field of view 6 onto a photosensitivedetector 20 including a plurality of pixels 22. The medical imagingdevice may also include features such as a light directing element 12and a filter 14. While a doublet lens arrangement has been depicted inthe figures, it should understood that other types of optics capable offocusing the field of view 6 onto the photosensitive detector 20 mightalso be used including, for example, fiber-optic bundles. Additionally,the photosensitive detector may correspond to a detector such as a CCD,a CMOS array, an APD array, or other appropriate detector.

With regards to the above noted embodiment, appropriate lenses for theobjective lens and imaging lens include, but are not limited to, animaging lens with a focal length between about 8 mm and 75 mm, and anobjective lens with a focal length between about 10 mm and 250 mm. Forexample, in one specific embodiment, an imaging lens has a focal lengthof 50 mm and an objective lens has a focal length of 40 mm for imagingLUM-1. In another possible embodiment, an imaging lens has a focallength of 200 mm and an objective lens has a focal length of 25 mm forimaging LUM 2.6. It should be understood that other focal lengths forthe imaging and objective lenses that are either greater than or lessthan the ranges noted above are also contemplated.

As illustrated in the figures, the medical imaging device may bepositioned such that a distal end of the rigid imaging tip 4 may bepressed against a surgical bed 24 including one or more cells 26 whichmay be marked with a desired imaging agent. Instances where all, aportion, or none of the cells are marked with the imaging agent arecontemplated. Pressing the rigid tip against the surgical bed mayprevent out of plane and lateral tissue motion, which may allow forcollection optics with larger f numbers and consequently, largercollection efficiencies, smaller blur radii, and smaller depth of field.Additionally, pressing the rigid imaging tip 4 against the surgical bedmay provide a fixed focal length between the tissue bed 24 andphotosensitive detector 20. In some embodiments, the rigid imaging tipmay have a length such that the distal end of the rigid imaging tip isalso located at a focal plane of the photosensitive detector 20.Therefore, pressing the rigid imaging tip against the surgical bed mayposition the surgical bed 24 and the cells 26 contained therein at thefocal plane of the imaging device. Depending on the particularembodiment, a distal end of the rigid imaging tip 4 may include a flatsurface to help position the surgical bed in the desired focal plane.However, in instances where an end of the rigid imaging tip is open, anappropriate depth of field (DOF) still may be provided to facilitateimaging of the tissue located within the field of view.

In some embodiments, it may be desirable to maintain a fixed distancebetween a distal end of the rigid imaging tip and the photosensitivedetector. This may help to maintain the focus of tissue located withinthe focal plane defined by the distal end of the rigid imaging tip.Therefore, the rigid imaging tip may be adapted to resist deflectionand/or deformation when pressed against a surgical bed such that tissuelocated within the focal plane defined by the distal end of the rigidimaging tip is maintained in focus. For example, a rigid imaging tip maydeflect by less than the depth of field of the medical imaging device inresponse to forces of about 5 lbf, 10 lbf, 15 lbf, 20 lbf, or any otherappropriate force. Appropriate materials for forming the rigid imagingtip include, but are not limited to, polycarbonate, acrylic, and BK7glass.

During use, the medical imaging device may be associated with anillumination source 18 that directs light 18 a with a first wavelengthtowards the light directing element 12. The first wavelength maycorrespond to an excitation wavelength of a desired imaging agent. Insome instances, the illumination source 18 may include appropriatecomponents to collimate the light 18 a. The illumination source 18 mightalso include one or more filters to provide a desired wavelength, orspectrum of wavelengths, while filtering out wavelengths similar tothose detected by the photosensitive detector 20. In some embodiments,the light directing element 12 may be a dichroic mirror with a cutoffwavelength that is greater than the first wavelength. Thus, the lightdirecting element 12 may reflect the incident light 18 a towards adistal end of the rigid imaging tip 4 and onto the surgical bed 24. Whenthe one or more cells 26 that are labeled with a desired imaging agentare exposed to the incident light 18 a, they may generate a fluorescentsignal 18 b that is directed towards the photosensitive detector 20. Thefluorescent signal may have a wavelength that is greater than the cutoffwavelength of the light directing element 12. Therefore, the fluorescentsignal 18 b may pass through the light directing element 12. The filter14 may be a band pass filter adapted to filter out wavelengths otherthan the wavelength of the fluorescent signal. Alternatively, the filter14 may permit other selected wavelengths to pass through as well. Thefluorescent signal 18 b may also pass through an aperture 16 to theimaging lens 10. The imaging lens 10 may focus the fluorescent signal 18b, which corresponds to light emitted from the entire field of view,onto a plurality of pixels 22 of the photosensitive detector 20. In someinstances, the fluorescent signal 18 b may be focused onto a firstportion 28 of the photosensitive detector while second portions 30 ofthe photosensitive detector are not exposed to the fluorescent signal.However, it should be understood that in some embodiments, thefluorescent signal may be focused on to an entire surface of aphotosensitive detector as the disclosure is not so limited.

In some embodiments, a field of view of each pixel of the one or morepixels 22 of the photosensitive detector 20 may be selected such that itis less than or equal to a desired cell size. However, depending on theparticular photosensitive detector used, the one or more pixels 22 mayeither be larger or smaller than a desired cell size. Consequently, andas illustrated by FIGS. 1A and 1B, respectively, a fluorescent signal 18b emitted from a surgical bed may be magnified or demagnified by theimaging device's optics to provide a desired field of view for eachpixel 22. Additionally, in some embodiments, the optics may provide nomagnification to provide a desired field of view for each pixel 20. Forexample, in the case of a photosensitive detector including pixels thatare smaller than a single cell, an imaging device 2 may provide amagnification factor of about 0.1 to 0.5 inclusively, 0.2 to 0.3inclusively, or any other appropriate magnification factor to provide adesired number of pixels per cell.

Having generally described embodiments related to a medical imagingdevice and an associated rigid imaging tip, several specific embodimentsdirected to different types of rigid imaging tips are described in moredetail below with regards to FIG. 2A-5C.

FIGS. 2A-2C and 4A-4C generally depict embodiments of a medical imagingdevice 100 including a distally extending rigid imaging tip 102corresponding to a tube with an open inner diameter. The rigid imagingtip 102 may include a distal portion 104 and a proximal portion 106. Adistal end 104 a of the rigid imaging tip located on the distal portion104 may define a field of view for the imaging device. Additionally, theproximal portion 106 may be constructed to either be detachably orpermanently connected to a body 112 of the imaging device. Inembodiments where the proximal portion 106 is detachably connected tothe body 112, the connection may include, for example, a snap on, screwon, suction, or magnetic connection. This may provide multiple benefitsincluding, for example, easily and quickly changing a rigid imaging tipduring a surgical procedure as well as enabling the rigid imaging tip tobe removed and sterilized. Consequently, in some embodiments, the rigidimaging tip may also be made from materials that are compatible withtypical sterilization techniques such as various steam, heat, chemical,and radiation sterilization techniques.

Depending on the particular embodiment, a body 112 of a medical imagingdevice 100 may be constructed and arranged to be a handheld medicalimaging device. However, embodiments in which the medical imagingdevice, and/or the methods of use described herein, are applied to amedical imaging device that is not handheld are also possible. Asdepicted in the figures, the body 112 may include a light couplingsection 114 attached to a housing 116. The housing 116 may be adapted tomount a photosensitive detector 118 to the medical imaging device. Insome embodiments, the photosensitive detector 118 may include anappropriate data output 118 a for outputting data to an externalcontroller, not depicted. One or more light inputs 120 associated withone or more separate illumination sources, not depicted, may be coupledto the light coupling section 114 as depicted in the figures to providelight including at least a first excitation wavelength to the medicalimaging device 100.

Referring now to FIGS. 3A-3B and 5A-5B, the general arrangement ofcomponents within a medical imaging device 100 interior are described inmore detail. As depicted in the figures, the medical imaging device mayinclude a rigid imaging tip 102 corresponding to a member distallyextending from the body 112 with an optically transparent or hollowinterior. A distal end 104 a of the rigid imaging tip 102 may define afocal plane located at a fixed distance relative to the opticallycoupled photosensitive detector 118 located on a proximal portion of themedical imaging device. In one embodiment, the optics coupling the rigidimaging tip and the photosensitive detector may include an objectivelens 134 and an imaging lens 136 located between the rigid imaging tipand the photosensitive detector. The objective and imaging lenses 134and 136 may focus light emitted from within a field of view of the rigidimaging tip onto a surface 138 of the photosensitive detector 118including a plurality of pixels. A magnification provided by thecombined objective and imaging lenses 134 and 136 may be selected toprovide a desired field of view for each pixel. Again, the field of viewfor each pixel may be selected such that each pixel may correspond toone cell or less of a tissue being imaged. However, embodiments in whicheach pixel may correspond to more than one cell are also contemplated.

The medical imaging device 100 may also include one or more lightdirecting elements 124 located between the photosensitive detector 118and a distal end 104 a of the rigid imaging tip. For example, asdepicted in the figure, the light directing element 124 may be locatedbetween the objective lens 134 and the imaging lens 136. However, otherlocations within the medical imaging device including along the rigidimaging tip are also contemplated. The light directing element 124 maybe adapted to reflect light below a cutoff wavelength towards the distalend of the rigid imaging tip and transmit light above the cutoffwavelength towards the photosensitive detector 118. In the currentembodiment, the cutoff wavelength may be greater than an excitationwavelength of a desired imaging agent and less than an emissionwavelength of the imaging agent. While any appropriate structure mightbe used for the light directing element, in one embodiment, the lightdirecting element is a dichroic mirror.

In some embodiments, the medical imaging device 100 may include one ormore filters 130 located between the light directing element 124 and thephotosensitive detector 118. The one or more filters 130 may be adaptedto permit light emitted from an imaging agent to pass onto thephotosensitive detector while blocking light corresponding to excitationwavelengths of the imaging agent. Depending on the embodiment, the oneor more filters may either permit a broad spectrum of wavelengths topass or they may only permit the desired emission wavelength, or anarrow band surrounding that wavelength, to pass as the disclosure isnot so limited.

An aperture stop 132 including an appropriately sized aperture may alsobe located between the rigid imaging tip 102 and the photosensitivedetector 118. More specifically, the aperture stop 132 may be locatedbetween the light directing element 124 and the imaging lens 136.Depending on the embodiment, the aperture may have an aperture diameterselected to provide a desired f number, depth of field, and/or reductionin lens aberrations. Appropriate aperture diameters may range from about5 mm to 15 mm inclusively which may provide an image side f numberbetween about 3 to 3.5 inclusively. However, other appropriate aperturediameters and f numbers are also contemplated.

During use, a medical imaging device 100 may be coupled to a light input120 from an associated illumination source. The light input 120 may beany appropriate structure including, for example, fiber-optic cablesused to transmit light from an associated illumination source to themedical imaging device. The light input 120 may be associated withoptical elements such as an aspheric lens to help collimate lightdirected towards the light directing element 124. The light input 120may also be associated with one or more filters in order to provide adesired wavelength, or a spectrum of wavelengths. This wavelength, orspectrum of wavelengths, may correspond to one or more excitationwavelengths of a desired imaging agent used to mark abnormal tissue forimaging purposes. Depending on the particular embodiment, the lightinput 120 may either be associated with a single illumination source, orit may be associated with multiple illumination sources. Alternatively,multiple light inputs may be coupled to the medical imaging device toprovide connections to multiple illumination sources as the currentdisclosure is not so limited.

It should be understood that the above components may be provided in anydesired arrangement. Additionally, a medical imaging device may onlyinclude some of the above noted components and/or it may includeadditional components. However, regardless of the specific featuresincluded, an optical axis 140 of a medical imaging device may pass froma distal end 104 a of a rigid imaging tip 102 to a photosensitivedetector 118. For example, light emitted from within a field of view maytravel along an optical path 140 passing through the distal end 104 a aswell as the distal and proximal portions 104 and 106 of the rigidimaging tip. The optical path may also pass through a light couplingsection 114 and housing 116 including various optics to thephotosensitive detector 118.

During certain surgical procedures, a surgical site may be subjected tonatural movements from a patient such as breathing, the surgical sitemay present irregular surfaces, and/or sidewalls might be necessary foroperation within the surgical cavity. Consequently, in some embodimentsa medical imaging device may include a rigid imaging tip with a closedflat distal end that may be pressed against a surgical bed within asurgical site to help mitigate movement of the surgical bed relative tothe medical imaging device. However, it should be understood that aclosed rigid imaging tip might also be used for other purposes as well.In some embodiments, the medical imaging device may also be shaped andsized to facilitate insertion into a surgical site for specificsurgeries. One such embodiment is described in more detail below withregards to FIG. 2A-3B.

As depicted in the figures, a medical imaging device 100 may include arigid imaging tip 102 with a distal portion 104 and a proximal portion106. The distal portion 104 may include a distal end 104 a including anopening optically associated with a photosensitive detector 118.Depending on the embodiment, a window 108 may be disposed on, orintegrated with, the distal end 104 a of the rigid imaging tip. Ininstances where the window 108 is disposed on the distal end, it mayeither be directly disposed on the distal end of the rigid imaging tipor it may be indirectly disposed on the rigid imaging tip. The window108 may be transparent to both the excitation wavelengths provided by anassociated illumination source as well as wavelengths emitted from adesired imaging agent. However, embodiments in which the window 108 istransparent to other wavelengths as well are also contemplated. Whileany appropriate shape might be used depending on the particular opticsand algorithms used, in one embodiment, the window 108 may have a flatshape to facilitate placing tissue at a desired focal plane when it ispressed against a surgical bed.

In some embodiments, a rigid imaging tip 102 may also include a bend 110to facilitate access of a medical imaging device into a surgical site.For example, a distal portion 104 of the rigid imaging tip may be angledrelative to a proximal portion 106 of the rigid imaging tip. Anyappropriate angle between the proximal and distal portions to facilitateaccess to a desired surgical site might be used. However in oneembodiment, an angle α between the proximal and distal portions may bebetween about 25° to 65° inclusively. For example, a rigid imaging tipmay have an angle α that is equal to about 45°. In embodiments includingan angled distal portion, the rigid imaging tip 102 may also include alight bending element 122 adapted to bend an optical path 140 throughthe bent rigid imaging tip. Appropriate light bending elements include,but are not limited to, mirrors and prisms. It should be understood thatthe specific shapes and dimensions of the rigid imaging tip may beselected to facilitate use in specific surgeries. For example, a medicalimaging device may include a distal end 104 a with an opening thatdefines a focal plane with a field of view with a lateral dimensionbetween about 10 mm and 50 mm, though field of views with dimensionsboth greater than and less than those noted above are also contemplated.This lateral dimension may be a diameter, though geometrical shapesother than a circle might also be used. The rigid imaging tip may alsoinclude a distal portion with a length between about 10 mm and 65 mm. Inthe embodiment shown, this is the distance from the distal end 104 a tothe point where the optical path contacts the light bending element 122as depicted in the figure. Such an embodiment may be of particular usein breast surgeries, though it might also be used for other surgeriessuch as brain cancer surgeries, ovarian cancer surgeries, and othertypes of cancer surgeries as well.

In other embodiments, it may be desirable for a surgeon to be able toaccess abnormal tissue in real-time while imaging is taking place. Suchan embodiment may facilitate simultaneous identification and removal ofabnormal tissue because the surgeon may both identify abnormal tissue inreal-time and access it for excision at the same time. To facilitatesuch access, a rigid imaging tip may include an open distal end as wellas one or more openings located on a side of the rigid imaging tip toprovide surgical access to a surgical bed. One specific embodiment isdescribed in more detail below referring to FIGS. 4A-5B.

As depicted in the figures, a rigid imaging tip 102 may include a distalportion 104 and a proximal portion 106 coupled to the medical imagingdevice. The distal portion 104 may include a distal end 104 a with anopening 200 that provides access to an associated surgical bed and isalso in optical communication with the photosensitive detector 118. Oneor more openings 204 may be located on a side of the rigid imaging tipto permit surgical access to the surgical bed while still using themedical imaging device. It should be understood that the openings may belocated on any side of the rigid imaging tip such that a surgeon mayaccess the surgical bed through the opening 200 provided at the distalend of the rigid imaging tip. In one specific embodiment, at least onesupport 202 may distally extend from the proximal portion 106 to thedistal portion 104 of the rigid imaging tip. Further, the one or moreopenings 204 may be defined by the at least one support. For example, asshown in the figures, the distal portion 104, supports 202, and proximalportion 106 may be approximately shaped as a conical frustum where theproximal portion 106 has a smaller diameter than the distal portion ofthe rigid imaging tip 104. Further, three radially spaced supports 202may distally extend from the proximal portion to the distal portion todefine three openings 204 located between the radially spaced supports.While a specific arrangement in shape of the open rigid imaging tip hasbeen depicted, other embodiments including different arrangements ofthese components as well as different shapes are also possible. In oneembodiment, there is a single support or strut extending from theproximal portion 106 to the distal portion 104 and supporting the distalportion 104.

As described in more detail below, when using an open imaging tip, anassociated surgical bed may be exposed to ambient light. In order tocompensate for the ambient light, an associated illumination source maybe adapted to pulse so that exposures of the photosensitive detector forwhich the illumination source is on consist of a desired fluorescencesignal and an ambient light signal. Correspondingly, exposures of thephotosensitive detector for which the illumination source is off consistof an ambient light signal. The illumination source may either be pulsedfor every other exposure of the photosensitive detector or it may bepulsed at a different time period as the disclosure is not so limited.The signal corresponding to a fluorescence of a desired imaging agentmay then be isolated by subtracting exposures corresponding to ambientlight from exposures corresponding to both ambient light and the pulsedillumination source.

As noted above, a distal end of a rigid imaging tip may be used todefine a focal plane located at a fixed distance from an associatedphotosensitive detector. However, in some embodiments, a medical imagingdevice may include an appropriate focusing element 206 to adjust thefocal distance of the medical imaging device, see FIGS. 4A-4C. Thus, afocus of the medical imaging device might be selectively adjustedbetween a focal plane located at the fixed distance defined by thedistal end of the rigid imaging tip and a second focal plane located ata second focal distance beyond the distal end of the rigid imaging tip.This may beneficially provide a field of view that may be adjustedbetween a smaller field of view for close-up examination where a medicalimaging device may be placed in contact with tissue and a larger fieldof view for examination in a standoff mode where the medical imagingdevice may be held above the tissue being imaged. This may be beneficialin surgeries such as cervical cancer surgery where a surgical site mightbe on the order of about 20 cm across and it is desirable to detectabnormal tissue over both small and large length scales.

Without wishing to be bound by theory, in embodiments where a field ofview defined by an open rigid imaging tip is relatively large, tissuefrom a surgical bed may protrude past a desired focal plane defined by adistal end of the rigid imaging tip. This may result in the tissue beingout of focus due to insufficient depth of field. While it may bepossible to increase a depth of field of the medical imaging device, insome embodiments, an open rigid imaging tip may include one or moretissue restraining elements. As illustrated in FIG. 6, the tissuerestraining element 210 may be embodied by a bar extending across adistal end 104 a of the rigid imaging tip. The restraining element mightalso correspond to a bar that extends across only a portion of thedistal end, a circular element located within an interior region of thedistal end, or any other feature capable of restraining tissue fromprotruding into the rigid imaging tip. Depending on the embodiment, thetissue restraining element 210 may be transparent to the excitationwavelength from a light source and a corresponding fluorescence emissionwavelength from a desired imaging agent.

In other embodiments, a rigid imaging tip may also incorporate anorienting feature 212 to help orient a surgeon relative to a surgicalsite being imaged by the medical imaging device, see FIG. 7. While anyappropriate feature might be used, in one embodiment, the orientingfeature 212 may correspond to a tab extending inwards from an interiorsurface of the rigid imaging tip such that it extends into the field ofview of the medical imaging device. Thus, the orienting feature mayprovide a visual guide within the surgical bed to help guide a surgeon.Additionally, as described in more detail below, the orienting feature212 may also be used to determine if the medical imaging device is infocus or not. While an orienting feature located within the rigidimaging tip has been depicted in the figures and described above,embodiments in which the orienting feature is located in a position thatis not visible to a surgeon while still providing an orienting featurein an image displayed by the device is possible. Additionally,embodiments in which software creates an orienting feature within animage output to an appropriate display without the presence of anorienting feature located in the device is also contemplated.

FIG. 8A-8D depict one embodiment of an illumination source 300. Theillumination source may include an LED 302 optically coupled to a lightinput 120 adapted for outputting light to an associated medical imagingdevice. As noted previously, the light input 120 may correspond to afiber-optic guide adapted for coupling to the associated medical imagingdevice. The LED 302 may be disposed on top of a heat sink 304 and one ormore cooling elements 306, such as one or more fans, may be used toremove heat from the illumination source. The LED may also be associatedwith an appropriate temperature sensor 308 adapted to sense atemperature of the LED for use by an associated controller. As notedabove, the LED 302 in one embodiment corresponds to a 50 W LED capableof providing 5.6 W of light with a wavelength of about 630 nm. Such anillumination source may be of particular benefit where a medical imagingdevice is comparing a fluorescence threshold of healthy tissue to afluorescence threshold of abnormal tissue due to the relatively highillumination intensity. However, embodiments in which a lower, orhigher, intensity illumination source may be used are also contemplated.For example, embodiments in which there is less tissue variabilitybetween patients for a particular type of surgery and an absoluteabnormal tissue threshold has been determined, a lower intensityillumination source might be used. Additionally, an illumination sourcemay provide any desired wavelength, or spectrum of wavelengths, as thedisclosure is not so limited.

Having generally described the various embodiments of a medical imagingdevice, various methods of use are described in more detail below.

FIG. 9A depicts one possible way in which a medical imaging device mightbe used. As indicated in the figure, tissue may be marked with anappropriate imaging agent at 400. The imaging agent may be provided inany appropriate fashion including, for example, injection and/or topicalapplication. A medical imaging device may optionally prompt a user toinput patient information at 402. The patient information might includeinformation such as a name, patient identification number, type ofsurgical procedure being performed, type of imaging agent being used,and other appropriate information. In some instances, a medical imagingdevice controller may incorporate warnings when required data fields arenot completed. However, user overrides might be used to proceed withimaging in instances where patient information is either unavailable orconfidential.

In some embodiments, it may be desirable to calibrate a medical imagingdevice prior to usage as indicated at 404. This may be done prior toevery usage, or it may only be done occasionally as needed to confirmcalibration as the disclosure is not so limited. While any appropriatecalibration method might be used, in one embodiment, calibration of amedical imaging device might include prompting a user to test a signalbrightness generated by a medical imaging device by imaging afluorescence standard and comparing the average value of that image to adefault standard value. Appropriate fluorescent standards may includeacrylonitrile butadiene styrene (ABS), though other fluorescentstandards might also be used. A medical imaging device control may alsoprompt a user to determine the system dark noise by imaging a darkstandard and/or covering the medical imaging device with a cover. Theaverage pixel value may then be compared to a default value. Thecontroller may then correct for both the dark noise and backgroundvariations in real time. The controller may also perform a smoothingoperation on an image of the fluorescent standard and may subsequentlyuse that image to correct images during real-time capture. A specificcorrection method is described in more detail below in the examples.

In some embodiments, the controller may only display pixels within apredefined field of view of the medical imaging device. Pixels locatedoutside of the field of view may be assigned a preset value including,for example, a value of zero. Pixels located outside of the field ofview may be determined by a signal cutoff value based on the fluorescentstandard image noted above. Pixels that fall below the cut off value maybe determined as being outside of the field of view.

As part of calibrating a medical imaging device, in some embodiments itmay be desirable to confirm a focus and resolution of the medicalimaging device prior to use. In such an embodiment, a controller of themedical imaging device may identify the location of a constant feature,such as an orienting feature protruding into the field of view and/or anedge of the field of view of the medical imaging device for evaluatingthe focus. A standard signal corresponding to the feature and/or edge ofthe field of view may be stored within a controller of the medicalimaging device. The standard signal may have a characteristic lengthover which a signal corresponding to the of the field of view and/or theconstant feature transitions when in focus. Consequently, when imaging astandard as noted above, the controller may compare a transition lengthassociated with an edge of the field of view and/or the constant featureto the previously determined characteristic length. If the imagedtransition length is different from the characteristic length, a usermay adjust the focus manually. Alternatively, in some embodiments, thecontroller of the medical imaging device may automatically adjust thefocus. While focusing may confirmed and adjusted during calibration, insome embodiments, focus may be adjusted during imaging of a surgical bedas well.

It should be understood that the various corrections noted above mayeither be performed individually or in combination.

After calibrating the medical imaging device, in some embodiments, acontroller may prompt a user to determine a normal tissue signal at 406.A normal tissue signal may be determined by having a user place a rigidimaging tip of the device at a known portion of healthy tissue andcollecting an image. A fluorescent signal corresponding to the normaltissue may then be captured by the medical imaging device to establishthe normal tissue signal for subsequent usage. While a single normaltissue signal obtained from a single image might be used, in someembodiments, a controller may determine an average normal tissue signalusing an average of several images of normal tissue.

The medical imaging device may also determine an abnormal tissuethreshold at 408. In some embodiments, an abnormal tissue threshold maybe determined by setting a value that is a predetermined amount greaterthan the normal tissue signal. However, in other embodiments, theabnormal tissue threshold may simply correspond to a known absolutethreshold corresponding to a particular imaging agent and tissue beingimaged. For example, an abnormal tissue threshold for breast cancerusing LUM015 may be greater than about 16.6×10¹⁰ counts/s/cm². Thisabnormal threshold was determined using a normal tissue signal of about11.2×10¹⁰ counts/s/cm² with a standard deviation of about 1.8×10¹⁰counts/s/cm². A corresponding mean abnormal tissue threshold was alsodetermined to be about 55.7×10¹⁰ counts/s/cm². Therefore, the abnormaltissue threshold is about three standard deviations higher than thenormal tissue signal while still being greatly less than the identifiedabnormal tissue threshold. While a particular threshold has beenindicated above for a particular surgery, the abnormal tissue thresholdlimit could be any appropriate value for a given imaging agent andtissue being imaged.

In instances where a user notices that a medical imaging device is notcompletely identifying regions of abnormal tissue, it may be desirableto adjust the abnormal tissue threshold to appropriately identify theabnormal tissue. In such an embodiment, determining an abnormal tissuethreshold may also include permitting a user to adjust the abnormaltissue threshold using a numerical input, slider provided on a graphicaluser interface, or other appropriate input. In order to prevent falsenegatives, it may be desirable to only permit lowering of the abnormaltissue threshold. Without wishing to be bound by theory, this wouldincrease the chance of false positives while limiting the chance offalse negatives.

After appropriately setting up a medical imaging device and measuring anormal tissue signal and/or abnormal tissue threshold, a medical imagingdevice may then be used to image a surgical bed or other tissue section.As indicated at 410, the medical imaging device may provide light from afirst illumination source to an associated surgical bed. The lightprovided by a first illumination source may include an excitationwavelength of an imaging agent used to mark the tissue as noted above.The medical imaging device may then collect a fluorescence signalemitted from the imaging agent located in the tumor using an appropriatephotosensitive detector at 412. In some embodiments, collecting thefluorescence signal from the surgical bed may also include collecting anautofluorescence signal from tissue located within the surgical bed. Thecollected fluorescence signal may be compared to the abnormal tissuethreshold at 414. Pixels of the photosensitive detector withfluorescence signals that are greater than the abnormal tissue thresholdmay be identified as corresponding to abnormal tissue. In someembodiments, a size of one or more contiguous pixels with fluorescencesignals that are greater than abnormal tissue threshold may optionallybe compared to a size threshold at 416 such that sizes greater than thesize threshold may be identify as abnormal and sizes less than the sizethreshold may be disregarded. This size threshold may correspond tosizes that are less than a corresponding cell size. However, sizethresholds that are larger than a corresponding cell size are possible.For example, the size threshold may be between about 5 μm and 160 μm, 5μm and 30 μm, 5 μm and 50 μm, or any other appropriate size. Sizethresholds both greater than and less than the ranges noted above arealso contemplated.

After identifying one or more areas within a field of view correspondingto abnormal tissue, a controller of a medical imaging device may bothoutput an image to an appropriate viewing device and indicate areascorresponding to abnormal tissue at 418. For example, the controllermight output an image to a viewing screen and it may indicate locationsof abnormal tissue depicted on the screen by highlighting or using ageometric shape. In one specific embodiment, the controller mayhighlight abnormal tissue corresponding to a size that is greater thanabout 2 mm² and may use a geometric shapes such as an arrow, a circle, asquare, a rectangle, a non-symmetric closed loop, or other appropriateshape to indicate abnormal tissue corresponding to a size that is lessthan about 2 mm² that would be difficult for a surgeon to visuallyidentify. It should be understood that different sizes for indicatingareas of abnormal tissue either greater than or less than 2 mm² are alsopossible.

It should be understood that a medical imaging device operated in theabove-noted matter may continuously provide excitation light to asurgical bed, collect the resulting fluorescence signals, identify areasof abnormal tissue and indicate the location of those identified areasof abnormal tissue to a user. Therefore, a surgeon may be able to viewreal-time images indicating the presence, or lack thereof, of abnormaltissue within a surgical bed without the need for lengthy testing ofexcised tissue samples. In some embodiments, the controller of themedical imaging device may also provide for either video and/or picturecapture to aid in performing and/or documenting a surgical procedure.

FIGS. 9B and 9C depict two other methods for operating a medical imagingdevice. Similar to the above, these methods may include marking tissuewith a first imaging agent. Additionally, as above, a medical imagingdevice may optionally acquire patient information, calibrate the medicalimaging device, and optionally obtain a normal tissue signal as well asan abnormal tissue threshold. The medical imaging device may thenidentify areas of abnormal tissue as described in more detail belowprior to indicating one or more contiguous pixels as corresponding toabnormal tissue.

FIG. 9B depicts a method for mitigating a large autofluorescence signalfrom adjacent normal tissue. However, such a method might also be usedin instances where a large autofluorescence signal is not present as thedisclosure is not so limited. In the depicted method, two or moreillumination sources may be alternatingly pulsed to provide light to asurgical bed at 420. The two or more illumination sources may providelight including two or more different excitation wavelengths of anassociated imaging agent. For example, a first illumination source mayprovide a first excitation wavelength and a second illumination sourcemay provide a second excitation wavelength. In embodiments where a lightdirecting element, such as a dichroic mirror, is used, the excitationwavelengths may be less than a wavelength cutoff of the light directingelement. In some embodiments, additional illumination sources, such as athird illumination source, may be used to provide additional excitationwavelengths. Regardless of the particular number of illumination sourcesused, the two or more illumination sources may correspond to anyappropriate structure. For example, two different color LEDs, lasers, orspectrally filtered lamps might be used. Additionally, the illuminationsources might be integrated into a single system, such as a singlelightbox, or they may be integrated into separate systems. The pulsingof the two or more illumination sources may be controlled such that theyare triggered for every other exposure of an associated photosensitivedetector though other timings for the pulses are also contemplated.

An associated photosensitive detector may collect the fluorescencesignals emitted from the surgical bed corresponding to the separateillumination sources at 422. A controller of the medical imaging devicemay then compare a fluorescence signal intensity and/or wavelength shiftin the detected signal of each pixel between the separate exposures.This signal shift may then be correlated to the expected shift from thefirst excitation wavelength to the second excitation wavelength for theassociated imaging agent. Pixels exhibiting the expected signal shiftmay then be identified as correlating to abnormal tissue.Correspondingly, pixels that do not exhibit the expected signal shiftmay be identified as correlating to normal tissue. Similar to the above,the controller may optionally compare a size of one or more contiguouspixels exhibiting the expected signal shift to a size threshold to alsodetermine if the identified pixels correspond to abnormal tissue.

FIG. 9C depicts a method for mitigating interference from ambient lightbeing reflected from within a surgical site being imaged. Such a methodmay be used with any medical imaging device, but in one embodiment, amedical imaging device including an open rigid imaging tip may employsuch a method. As indicated in the figure, ambient light may be providedto a surgical bed at 428. The ambient light may either be incident uponthe surgical bed because a medical imaging device is being operated in astandoff mode and/or because an imaging tip of the device includesopenings for surgical access through which the light enters. Anillumination source adapted to provide an excitation wavelength of theimaging agent may be pulsed to deliver light to the surgical bed at 430.While the illumination source may be pulsed in any appropriate, in oneembodiment, the illumination source may be pulsed every other exposureof an associated photosensitive detector. The photosensitive detectormay then collect a combined fluorescence and ambient light signalemitted from the surgical bed during one exposure at 432. Separately,the photosensitive detector may collect an ambient light signal emittedfrom the surgical bed during another exposure at 434 when theillumination source is off. A controller of the medical imaging devicemay then subtract the ambient light signal from the combinedfluorescence and ambient light signal to produce a fluorescence signalat 436. The fluorescence signal for each pixel of the photosensitivedetector may then be compared to an abnormal tissue threshold andoptionally a size threshold to identify the presence of abnormal tissueas previously noted.

FIG. 19 depicts one embodiment of a graphical user interface used forindicating the location of abnormal tissue 702 relative to normal tissue700. As shown in the figure, in addition to showing a real time image808 indicating the location of abnormal tissue as described above, thegraphical user interface may include buttons for initiating proceduressuch as patient data acquisition 800, calibrating the system against afluorescent standard 802, calibrating a normal tissue signal 804, andadjustment of an abnormal tissue threshold 806. The interface may alsoinclude buttons for saving videos 810 and images 812. One or moresmaller screen shots 814 from the saved videos and images may also bedisplayed on a screen to aid a surgeon in keeping track of multiplelocations within a surgical bed, the progress of a surgery over time, orother appropriate use. It should be understood that other arrangementsmight also be used.

Having generally described a medical imaging device and its methods ofuse above, several non-limiting examples of its application andimplementation are provided below.

Example Autofluorescence Mitigation

FIGS. 10A and 10B present graphs of emission intensities for twoseparate fluorphores, mPlum and cy5, exposed to different excitationwavelengths. As shown in FIG. 10A the shift in excitation wavelengthyielded a decrease in emission intensity of about 96% for fluorphore 1which was mPlum. Additionally, a shift in excitation wavelength yieldedan increase in emission intensity of about 156% for fluorphore 2 whichwas cy5. As noted above, this shift in emission intensity in response todifferent excitation wavelengths can be used to identify a particularfluorphore surrounded by autofluorescing tissue that exhibits adifferent shift in emission intensity and/or wavelength in response tothe same excitation wavelengths.

Example Correcting for Ambient Light

FIG. 11A-11C illustrate a method for identifying a fluorescence signalin the presence of ambient light. In FIG. 11A a surface including afluorescent material is subjected to both ambient light and anexcitation wavelength generating an ambient light signal andfluorescence signal. Subsequently, the surface is exposed to justambient light as illustrated in FIG. 11B. The image captured in FIG. 11Bcorresponding to just an ambient light signal may then be subtractedfrom FIG. 11A corresponding to an ambient light and fluorescence signal.The resulting image is presented in FIG. 11C where the bright featureindicated in the figure corresponds to the fluorescence signal.

Example Medical Imaging Device Characteristics

Exemplary characteristics form medical imaging devices used duringinitial studies are provided below in Table I. The providedcharacteristics include image side f-number, object side f-number,illumination flux, excitation wavelength, emission wavelength, objectivelens focal length, and imaging lens focal length. It should beunderstood that different values of these physical characteristics thanthose presented below might also be used.

TABLE I Objec- Im- Excita- Emis- tive aging Illum. tion sion lens lensImage Object Flux Wave- wave- focal focal De- side f/# side f/# mW/length length length length vice unitless Unitless cm² nm nm mm mm 1 3.34.17 172 628-672 685-735 50 40 2 3.0 13.3 64 590-650 663-738 200 25

Example Standard Calibration

FIG. 12A-12C depict the imaging and analysis of a acrylonitrilebutadiene styrene (ABS) fluorescent standard imaged with a medicalimaging device. Alternatively, the standard might correspond to aquantum dot (QD) plate or other appropriate material. The fluorescencesignals from an ABS fluorescent standard and a QD plate standard asmeasured with the devices 1 and 2 described above are shown in Table IIbelow. Due to the particular construction of the device, the measuredsignals are reported in counts/s/cm².

TABLE II Device QD Plate (10¹⁰ counts/s/cm²) ABS (10¹⁰ counts/s/cm²) 15.8 7.4 2 35 8.8

FIG. 12A is a raw image of an ABS standard. FIG. 12B presents the countsper pixel across a width of the image. As illustrated in the figure,pixels corresponding to the field of view 500 have a count value that isgreater than a threshold number of counts per exposure. Pixels that havea number of counts that is less than the threshold number of counts perexposure can this be determined to be outside the field of view. Acontroller and medical imaging device may then set a value of the pixels502 outside of the field of view to a preset value such as zero asillustrated in FIG. 12C.

In addition to using an image of the fluorescent standard to determinethe field of view, a dark noise image may be taken for additionalcalibration purposes. Values associated with the dark noise image aredependent upon the exposure length. Therefore, the exposure length ofthe dark field image may be correlated with the exposure length expectedduring use of a medical imaging device. Without wishing to be bound bytheory, the dark noise associated with each individual pixel includesboth a time dependent and time independent component. Depending on theparticular embodiment, the dark noise value associated with each pixelmay be determined by capturing a dark noise image with a proper exposurelength. Alternatively, the time independent component may be added tothe time dependent component of the dark noise value integrated over thedesired exposure time.

As noted above, images captured by a medical imaging device may becorrected using the dark noise and fluorescent standard images. Morespecifically, the fluorescence standard image (I_(FS)) may be smoothedusing a simple, running-window average, and then normalized by themaximum fluorescence signal within the standard image [max(I_(FS))]. Thedark noise image (I_(DN)) may then be subtracted from the real-timeimage (I_(RT)) being captured by the medical imaging device during use.The normalized fluorescence standard image may then be divided out ofthe “dark noise” corrected image to produce the output image (I_(out)).A representative formula is provided below. However, it should beunderstood that other methods of calibrating a medical imaging deviceand correcting an image are also possible.

$I_{out} = \frac{I_{RT} - I_{DN}}{I_{FS}/{\max ( I_{FS} )}}$

Example Focus

FIG. 13A-15B depict the imaging and analysis of a acrylonitrilebutadiene styrene (ABS) fluorescent standard imaged with a medicalimaging device while in focus and out of focus. FIG. 13A is a raw imageof a fluorescent standard in focus and FIG. 13B is a raw image of afluorescent standard autofocus. The images were taken with device 2 asdescribed above. Lines 600 and 602 represent the slices along which thesignals presented in FIGS. 14A and 14B were taken. FIGS. 14A and 14Bdepict a standard signal profile across the raw image for both a focusedand unfocused image. However, as shown in the zoomed in FIGS. 15A and15B a transition length between the pixels located at an edge of thefield of view and the pixels located outside the field of view changesfrom between about 80 μm to 160 μm for the in focus image to atransition length that is greater than 310 μm for the presented image.Therefore, the controller of the medical imaging device used a thresholdtransition length of 160 μm. However, it should be understood that theparticular transition length, or range of transition lengths, used for aparticular imaging device will depend on the optics and focal distancesbeing used.

Example Imaging of a Dog with Naturally Occurring Lung Cancer

A dog with naturally occurring lung cancer was injected with LUM015 andsubsequently imaged intraoperatively using a medical imaging device. Thefluorescence image from the tumor is depicted in FIG. 16A. Thefluorescence signal corresponding to abnormal tissue present within thetumor is clearly visible. This is contrasted with the image of normallung tissue depicted in FIG. 16B where virtually no fluorescence signalwas observed. The tumor to background ratio determined using theseimages was about 3 to 1.

Example Indicating Locations of Abnormal Tissue

FIGS. 17A and 18A are raw images taken of a mouse-sarcoma surgical bedafter surgery in a mouse following IV injection of LUM015. FIGS. 17B,17C and 18B illustrate several different ways that abnormal tissue 702may be indicated relative to normal tissue 703. More specifically, FIGS.17B and 17C illustrate indicating the location of abnormal tissuethrough the use of appropriate indicating geometry such asnon-symmetrical closed loops following a periphery of the abnormaltissue. In contrast, FIG. 18B illustrates indicating the location ofabnormal tissue by highlighting that tissue with an appropriatelycontrasting color such as red, green, purple, yellow, or other desiredcolor. In either case, the presented images may indicate the presence ofthe abnormal tissue to a surgeon to aid in a surgical procedure.

Example Comparison of LUM033 and LUM015 in Mice

Table III presents test results performed on mice using differentimaging agents to image a soft tissue sarcoma. The resulting ratios oftumor to muscle signal observed were approximately 6.9 for LUM015 and6.3 for LUM033.

In addition to the above, and without wishing become by theory,cathepsin and MMP measurements in mice are significantly lower in micetumors than in human tumors and as expected the benefit of the tri-modeprotease activated probe was reduced. Therefore, the tumor and musclesignals in LUM015 were about one half that of LUM033 due in part to thelower levels of protease expression in the murine models. Consequently,improved signal generation associated with LUM015 is expected in humans.

TABLE III Tumor Imaging Dose Signal Muscle Signal Ratio of Tumor agent(mouse) ×10¹⁰ ×10¹⁰ to Muscle Signal LUM015 3.5 mg/kg 36 ± 15 5.2 ± 1.96.9 (n = 15) LUM033 3.5 63 ± 18  10 ± 3.4 6.3 (n = 11)

Example Performance in Mice, Dogs, and Humans Across Cancer Types

Table IV presents sensitivity, specificity, and tumor to normal tissuesignal ratios for several types of tissues in mice, dogs, and humans. Asillustrated by the data below, the medical imaging devices describedherein coupled with appropriate imaging agents are able to obtain superbsensitivity and specificity across these species and several cancertypes.

TABLE IV Tumor-to- Species and Sensitivity and normal tissue cancer typeEndpoint Specificity signal ratio Humans (n = 25) Pathology of 89%, 88%5:1 resected tissue Dogs with lung, Pathology of 93%, 91% 7:1 mammarygland, resected tissue sarcoma, mast and negative cell tumors margins (n= 12) Mice with Pathology of 90%, 80% 8:1 sarcoma (n = 18) resectedtissue Mice with Local 80%, 80% 8:1 sarcoma (n = 34) recurrence Micewith breast Pathology of 100%, 100% 8:1 cancer (n = 44) resected tissue

Example Initial Human Trials

Nine patients (8 sarcoma patients and 1 breast cancer patient) wereinjected intravenously with LUM015 (3 with 0.5 mg/kg and 6 with 1 mg/kg)and then underwent standard surgery and the resected tissue was imagedat a pathology suite. No adverse events were observed in the patients.Resected tissues from the patients were imaged and an averagetumor-to-background signal ratio of about 5 to 1 with a sensitivity ofabout 80% and specificity of 100% was measured. Interestingly, in thefirst patient, there was a nodule that the pathologist identified as alymph node upon visual examination. However, the nodule had activatedthe imaging agent and later was shown by histopathology to be a sarcoma.

While the present teachings have been described in conjunction withvarious embodiments and examples, it is not intended that the presentteachings be limited to such embodiments or examples. On the contrary,the present teachings encompass various alternatives, modifications, andequivalents, as will be appreciated by those of skill in the art.Accordingly, the foregoing description and drawings are by way ofexample only.

What is claimed is:
 1. The handheld medical imaging device of claim 25wherein the focal plane at the distal end of the rigid imaging tip is ata fixed focal distance relative to the photosensitive detector, andwherein the distal end of the rigid imaging tip is constructed to beplaced in contact with tissue and maintain the tissue at the focalplane. 2-3. (canceled)
 4. The handheld medical imaging device of claim27, wherein the threshold wavelength is less than an emission wavelengthof a preselected imaging agent and greater than an excitation wavelengthof the preselected imaging agent.
 5. The handheld medical imaging deviceof claim 4 wherein the excitation wavelength and emission wavelength areboth between about 590 nm and 850 nm inclusively.
 6. The handheldmedical imaging device of claim 4 wherein the excitation wavelength andemission wavelength are both between about 300 nm and 1,000 nminclusively.
 7. The handheld medical imaging device of claim 27, whereinthe threshold is greater than a first excitation wavelength of a firstillumination source associated with the light directing element. 8-14.(canceled)
 15. The handheld medical imaging device of claim 14, whereinthe optics magnify the field of view.
 16. The handheld medical imagingdevice of claim 14, wherein the optics demagnify the field of view. 17.The handheld medical imaging device of claim 14, wherein the opticsinclude an aperture with a diameter between about 5 mm to 15 mminclusively.
 18. The handheld medical imaging device of claim 14,wherein the optics include an objective lens and an imaging lens. 19.The handheld medical imaging device of claim 14, wherein a depth offield of the optics is between about 0.1 mm to 10 mm inclusively. 20-21.(canceled)
 22. The handheld medical imaging device of claim 25, whereinthe distal end of the rigid imaging tip is open, and wherein the rigidimaging tip includes at least one opening on a side of the rigid imagingtip to provide surgical access to the distal end of the rigid imagingtip.
 23. The handheld medical imaging device of claim 25, wherein therigid imaging tip includes at least one orienting feature extending intothe field of view.
 24. The handheld medical imaging device of claim 25,further comprising a focusing element adapted to change a focus of thephotosensitive detector from the fixed focal distance to a second focaldistance located beyond the distal end of the rigid imaging tip.
 25. Ahand held medical imaging device comprising: an imaging device body; arigid imaging tip distally extending from the imaging device body,wherein a distal end of the rigid imaging tip defines a focal plane witha field of view with a lateral dimension between about 10 mm to 50 mminclusively, and wherein the rigid imaging tip includes a proximalportion and a distal portion that is angled by about 25° to 65°inclusively relative to the proximal portion, wherein a length of thedistal angled portion is between about 10 mm to 65 mm, and wherein anoptical axis passes through the rigid imaging tip from the distal end ofthe rigid imaging tip to the proximal end of the rigid imaging tip. 26.The handheld medical imaging device of claim 25, further comprising aphotosensitive detector optically associated with the rigid imaging tip,wherein the photosensitive detector comprises a plurality of pixels. 27.The handheld medical imaging device of claim 26, further comprising alight directing element positioned between the photosensitive detectorand the rigid imaging tip, wherein the light directing element isadapted to reflect light below a threshold wavelength towards the distalend of the rigid imaging tip and transmit light above the thresholdwavelength towards the photosensitive detector.
 28. The handheld medicalimaging device of claim 26, further comprising optics located betweenthe photosensitive detector and the rigid imaging tip, wherein amagnification of the optics provide a field of view between about 5 μmto 100 μm for each pixel of the plurality of pixels.
 29. The handheldmedical imaging device of claim 25, wherein the lateral dimension of thefield of view is a diameter.
 30. The handheld medical imaging device ofclaim 25, wherein the distal end of the rigid imaging tip includes aflat window transparent to preselected wavelengths.
 31. The handheldmedical imaging device of claim 25, further comprising a mirror or prismlocated within the rigid imaging tip that bends the optical path suchthat it passes through the proximal portion and the distal angledportion of the rigid imaging tip.
 32. The handheld medical imagingdevice of claim 25, wherein the handheld medical imaging device is ahandheld breast surgery imaging device. 33-44. (canceled)
 45. The handheld medical imaging device of claim 25, wherein the rigid imaging tipincludes a first portion and a second portion including the distal end,wherein the distal end includes an opening to provide access to asurgical bed, and wherein one or more supports extend between the firstportion and the second portion.
 46. The handheld medical imaging deviceof claim 45, wherein the one or more supports define at least oneopening disposed on a side of the rigid imaging tip. 47-70. (canceled)